The official charge was for insolence shown towards the Dynasty, but it was clearly a measure designed to put the King’s vassals back under control of the central authority. The method of execution was diagnostic (also somewhat… Byzantine):
Kim Chol, vice minister of the army, was taken into custody earlier this year on the orders of Kim Jong-un, who assumed the leadership after the death of his father in December.
On the orders of Kim Jong-un to leave “no trace of him behind, down to his hair,” according to South Korean media, Kim Chol was forced to stand on a spot that had been zeroed in for a mortar round and “obliterated.”
Note that I had to translate the titles: North Korea until quite recently was under a form of government known as Communism, which was quite popular in the last century despite the fact that it apparently makes its adherents abjectly stupid – and murderous, when possible. Its ongoing evolution to hereditary monarchy is, of course, an improvement, but you have to expect a certain amount of barbarism in the process (it is uncertain whether this judicial murder was ordered by the King himself, or his uncle the Grand Vizier). I would suggest that the remaining members of the North Korean baronages would find it well-advised to create some sort of united front to establish their rights and prerogatives; after all, as it currently stands King Jong-un can simply kill them off one by one. If the barons need some ideas, this might prove to be a useful primer: I’m sure that somebody can translate it into Korean for them.
PS: Once they get the King to agree to terms, I further suggest that the barons work with him to establish a permanent institution by which the North Korean monarchy and aristocracy can communicate and/or negotiate with each other. Something like their current ‘Party Congress,’ only with actual teeth…